A loudspeaker is a transducer that produces sound in response to an electrical audio signal input. The vast majority of loudspeakers in use today are electromagnetic transducers. Referred to as dynamic loudspeakers, this class has essentially remained unchanged since the 1920's. Typically, a linear motor, such as an electromagnetic or electrostatic motor, actuates a diaphragm, which causes sound waves to be emitted by the speaker.
More recently, a new class of mechanical-transducers has been developed. Those transducers may have an actuator that may be coupled to an edge of a speaker diaphragm or diaphragm that may be anchored and spaced from the actuator. In such transducers, the transducer is typically a piezoactuator. Mechanical motion of the actuator is translated into movement of the diaphragm, generally in a direction that is transverse to the direction of motion of the actuator. The diaphragm radiates acoustic energy. Mechanical-to-acoustical transducers are exemplified in each of U.S. Pat. Nos. 6,720,708 and 7,038,356.
A problem with that new class of mechanical-acoustical transducers is durability. For example, the piezoelectric transducer includes a ceramic component that can be easily damaged, in particular through excessive strain due to impact forces.